Abstract: Disclosed herein are methods and systems for monitoring fluid flow in a rock formation that include utilizing a tracer fluid containing a homogeneous dispersion of ultrastable magnetic nanoparticles which can be injected into the rock formation. A series of EM signals can be emitted in formation by a transmitter at a first plurality of discrete depths along a first path, that can be recorded by a receiver at a second plurality of locations at a second plurality of discrete depth. The received EM signals can be processed to generate a set of EM permeability data that is indicative of variations in magnetic permeability between the first path and the second path. A magnetic permeability map can be generated that is indicative of a location of the tracer fluid.